If you only know оди́н as the number "one," you're missing most of its working life. оди́н·одна́·одне́·одні́ is one of the busiest words in Ukrainian: alongside counting, it acts as an indefinite "a certain" in narration, as "alone / only," as half of the "one… the other" and "some… others" contrasts, and — most surprisingly to English speakers — as the building block of the reciprocal "each other." It agrees in gender and number with its noun and declines through all seven cases. This page walks through each non-numeral use, keeps it apart from the cardinal "one," and untangles той са́мий "the same one" from одна́ковий "identical, alike." Because оди́н is so multifunctional, learners who think of it as just a number can't recognize it doing these jobs — so they sound either too literal or simply wrong.
оди́н 'a (certain)' — the storyteller's indefinite
In narration and reference, оди́н introduces a specific but as-yet-unidentified person or thing — exactly the English "a (certain)." This is the classic opening of folk tales and the natural way to bring a new specific referent on stage. It is not the number; it's an indefiniteness marker.
Жив собі́ оди́н коро́ль, і було́ в ньо́го три до́чки.
There once lived a king, and he had three daughters. — оди́н opens the tale: 'a (certain) king', not 'one king' as a count.
Оди́н мій знайо́мий розпові́в мені́ ціка́ву істо́рію.
An acquaintance of mine told me an interesting story. — оди́н знайо́мий = 'a certain acquaintance', a specific person I won't name.
Я зустрі́в одну́ жі́нку, яка́ зна́ла твою́ ба́бусю.
I met a (particular) woman who knew your grandmother. — одну́ flags a specific but unintroduced person.
The tell that this is the "a certain" use and not counting: you could replace English "a" / "a certain" for it, and there's no contrast with "two" or "three" intended. Compare the genuine numeral, where the count is the point:
У ме́не лиши́вся ті́льки оди́н квито́к.
I have only one ticket left. — here оди́н really counts: one, as opposed to two; the numeral, not the indefinite marker.
оди́н 'alone, only, by oneself'
оди́н also means "alone, on one's own, by oneself," agreeing with the person. This overlaps in feel with English "alone" and "by myself."
Я живу́ оди́н, але́ мені́ не само́тньо.
I live alone, but I'm not lonely. — оди́н = 'alone' (a man speaking; a woman would say одна́).
Вона́ зали́шилася одна́ в поро́жньому до́мі.
She was left alone in the empty house. — одна́ agrees with the feminine subject.
Не сиди́ оди́н ці́лий ве́чір — прихо́дь до нас.
Don't sit alone all evening — come over to us. — оди́н 'alone', here in the imperative addressed to a man.
In the dative and other oblique cases it still agrees: сиді́ти одному́ "to sit alone (masc.)," їй було́ ва́жко одні́й "it was hard for her on her own."
оди́н… і́нший / одні́… і́нші — 'one… the other', 'some… others'
оди́н sets up contrasts. In the singular, оди́н… і́нший (or дру́гий) means "one… the other." In the plural, одні́… і́нші (or дру́гі) means "some… others." Here одні́ is the plural of оди́н used as "some (of a set)."
Оди́н каза́в одне́, і́нший — зо́всім і́нше.
One said one thing, the other said something completely different. — оди́н... і́нший contrast in the singular.
Одні́ лю́ди лю́блять зи́му, і́нші — лі́то.
Some people love winter, others love summer. — одні́... і́нші, the plural 'some... others'.
Книжки́ лежа́ли скрізь: одні́ на по́лиці, і́нші про́сто на підло́зі.
Books lay everywhere: some on the shelf, others right on the floor. — одні́... і́нші sorting a set into groups.
This плюральне одні́ "some" is a real surprise to learners who only know оди́н as "one" — a plural of "one" looks like a contradiction until you see it means "some (members of a group)."
оди́н о́дного — the reciprocal 'each other'
This is the use English speakers least expect. Ukrainian builds "each other / one another" out of оди́н, by pairing оди́н (the subject-side half) with a case form of the same word (the object-side half). The two halves match the gender and number of the people involved:
| Who | Form | Example |
|---|---|---|
| males / mixed (default) | оди́н о́дного | лю́блять оди́н о́дного |
| females | одна́ о́дну | підтри́мують одна́ о́дну |
| neutral / mixed (modern) | одне́ о́дного | допомага́ють одне́ о́дному |
The second element takes whatever case the verb or preposition demands, while оди́н stays put as the "anchor." So "love each other" (accusative object) is оди́н о́дного, but "help each other" (dative object of допомага́ти) is одне́ о́дному, and "talk to each other" (after one з) is оди́н з о́дним.
Вони́ лю́блять оди́н о́дного зма́лку.
They've loved each other since childhood. — accusative о́дного after люби́ти; оди́н о́дного is the default reciprocal.
Сестри́ завжди́ підтри́мують одна́ о́дну.
The sisters always support each other. — all-female, so одна́ о́дну; accusative о́дну.
Вони́ допомага́ють одне́ о́дному в усьо́му.
They help each other with everything. — допомага́ти takes the dative, so о́дному; одне́... is the modern mixed-group form.
Ми бага́то ро́ків писа́ли оди́н о́дному ли́сти.
For many years we wrote each other letters. — dative о́дному after the recipient role.
Note the difference from the reflexive себе́ "oneself": себе́ is each person acting on themselves; оди́н о́дного is the two parties acting on each other. The full reciprocal system — including the -ся verbs that bundle "each other" into the verb (зустріча́тися, цілува́тися) — is on the reciprocal pronoun page.
той са́мий vs одна́ковий — two kinds of 'the same'
English "the same" is ambiguous, and Ukrainian forces a choice that оди́н is tangled up in:
- той са́мий (and the close оди́н і той са́мий) = "the same one" — one single, identical referent mentioned again. The very same car, person, day.
- одна́ковий = "identical, alike, of the same kind" — two different things that happen to be the same in form or quality.
Це той са́мий буди́нок, де я ви́ріс.
This is the same house where I grew up. — той са́мий = one and the same building, re-identified.
У нас одна́кові телефо́ни.
We have identical phones. — одна́кові = two separate phones that are the same model; NOT one shared phone.
Ми прийшли́ до о́дного й того́ са́мого ви́сновку.
We came to one and the same conclusion. — оди́н і той са́мий, the emphatic 'the very same'.
Confusing them changes the meaning: той са́мий телефо́н is "the (one) same phone (we keep talking about)"; одна́ковий телефо́н is "a phone identical (to another)." Pick by whether you mean one referent re-mentioned (той са́мий) or two alike things (одна́ковий).
оди́н declines and agrees
Across all these uses, оди́н is not frozen — it agrees (оди́н masc., одна́ fem., одне́ neut., одні́ pl.) and declines through the cases (genitive одного́/одніє́ї, dative одному́/одні́й, instrumental одни́м/одніє́ю, etc.). So the "a certain," "alone," and reciprocal uses all inflect to fit the slot, exactly as you saw in the examples above (одну́ жі́нку, одному́, одніє́ї).
Source-language comparison
For an English speaker, the leap is realizing оди́н is not just a number. It does three jobs English spreads across different words: the storyteller's "a (certain)" (English "a"/"a certain"), "alone," and — with no English parallel in form — the reciprocal "each other," which English builds from "each + other" but Ukrainian builds by doubling оди́н and case-marking the second half. Two habits to install: use оди́н for the specific-indefinite "a certain" in narration (not for every "a"), and form "each other" as оди́н + case form, matched to the group's gender. Also keep "the same" sorted: той са́мий (one referent again) vs одна́ковий (two alike things).
For a Russian speaker, the uses parallel оди́н/оди́н... друго́й/друг дру́га, but mind the Ukrainian forms and contrasts: the reciprocal is оди́н о́дного / одна́ о́дну / одне́ о́дного (not the Russian construction), "the same one" is той са́мий, "alike" is одна́ковий, and the plural "some" is одні́. The grammar transfers; the lexical shapes and stress are Ukrainian.
Common Mistakes
❌ Вони́ лю́блять себе́. (meaning each other)
себе́ = each loves himself. For 'they love each other', use the reciprocal: Вони́ лю́блять оди́н о́дного.
✅ Вони́ лю́блять оди́н о́дного.
They love each other — оди́н о́дного, the reciprocal.
❌ Вони́ допомага́ють оди́н о́дного.
Wrong case — допомага́ти takes the dative, so the second half is о́дному, not о́дного: Вони́ допомага́ють одне́ о́дному.
✅ Вони́ допомага́ють одне́ о́дному.
They help each other — dative о́дному, as допомага́ти requires.
❌ У нас той са́мий телефо́н. (meaning identical phones)
той са́мий = ONE and the same phone. For two phones alike, use одна́ковий: У нас одна́кові телефо́ни.
✅ У нас одна́кові телефо́ни.
We have identical phones — одна́ковий for two alike things.
❌ Жив собі́ оде́н коро́ль.
Spelling/form error — the masculine is оди́н, not *оде́н. Use: Жив собі́ оди́н коро́ль.
✅ Жив собі́ оди́н коро́ль.
There once lived a king — оди́н as the storyteller's 'a (certain)'.
❌ Сестри́ підтри́мують оди́н о́дного.
Gender mismatch — for an all-female pair the reciprocal is одна́ о́дну, not оди́н о́дного: Сестри́ підтри́мують одна́ о́дну.
✅ Сестри́ підтри́мують одна́ о́дну.
The sisters support each other — одна́ о́дну, matched to the female pair.
Key Takeaways
- оди́н is far more than the number 'one'; it agrees in gender/number and declines across these jobs.
- 'A (certain)': the storyteller's specific-indefinite — Жив собі́ оди́н коро́ль, Оди́н мій знайо́мий…
- 'Alone / only': Я живу́ оди́н, зали́шилася одна́.
- Contrasts: оди́н… і́нший 'one… the other'; одні́… і́нші 'some… others' (plural одні́ = 'some').
- Reciprocal 'each other': оди́н о́дного, gender-matched to одна́ о́дну, одне́ о́дного; the second half takes the verb's case (допомага́ють одне́ о́дному).
- 'The same': той са́мий = one referent re-mentioned; одна́ковий = two alike things — don't swap them.
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- Expressing 'the' and 'a' Without ArticlesA2 — A practical toolkit for conveying English article distinctions in article-less Ukrainian. DEFINITE ('the'): put the known noun FIRST (Маши́на стої́ть бі́ля до́му 'the car is by the house') or use a demonstrative цей/той. INDEFINITE ('a'): put the new noun LATER (Бі́ля до́му стої́ть маши́на 'there's a car by the house'), use оди́н for 'a (certain specific)', or якийсь for 'some (vague)'. GENERIC: bare noun (Соба́ка — друг люди́ни). The workhorse is WORD ORDER + topic position, not a word — most of the time you add nothing.
- Ukrainian Has No ArticlesA1 — Ukrainian has no articles at all — no 'a', no 'an', no 'the'. A bare кни́га means 'a book', 'the book', or just 'book' depending entirely on context. Definiteness is carried not by a word but by WORD ORDER (new information drifts to the end: На столі́ кни́га 'there's a book on the table' vs Кни́га на столі́ 'the book is on the table'), by demonstratives (цей/той) when you truly need 'this/that', and by оди́н for 'a certain'. The fix for English speakers is to drop the article instinct entirely — don't reach for a word to translate 'a' or 'the'.
- Reciprocal 'Each Other' (Один Одного)B1 — Ukrainian says 'each other' with a two-word frame: a gender-matched оди́н / одна́ / одне́ that points at the group, plus a declining о́дного / о́дну that takes whatever case the verb or preposition demands. The construction inflects internally — оди́н о́дному (dat), оди́н з о́дним (instr), оди́н про о́дного (about each other) — and the preposition wedges between the two halves: оди́н до о́дного, оди́н на о́дного. Keep it apart from reflexive себе́ / -ся, which means 'on oneself', not 'on each other'.
- Numeral–Noun Agreement (The Hard Part)B1 — The notorious three-way rule: after 1 (and …1) the noun is nominative SINGULAR, after 2/3/4 (and …2/3/4) nominative PLURAL with the dual-reflex end-stress (два столи́, дві сестри́), and after 5+ genitive PLURAL — chosen by the LAST digit, and applying only when the whole phrase is nominative or inanimate-accusative.
- Determinative Pronouns (Весь, Сам, Кожен, Інший)B1 — The determinative pronouns are the quantifying words 'all/whole, oneself/the very, each/every, other, the same, not a single' — весь·вся·все·всі, сам·сама́·само́·са́мі, ко́жен, і́нший, той са́мий, жо́ден. They all decline and agree like adjectives. Two traps for English speakers: все 'everything' (neuter) vs всі 'everyone' (plural) are different words, and сам 'in person / by oneself' (Я сам це зроби́в) is NOT the reflexive себе́ — Я сам себе́ не розумі́ю uses both at once.